Storage and retrieval machines typically travel along an aisle between adjacent storage rack structures and have a base on which is mounted a mast supporting a lift carriage which is movable in vertical directions along the mast. A shuttle is mounted on the carriage and the carriage and shuttle together carry a load object to be stored in or retrieved from a rack of the storage structure. The shuttle includes telescoping plate members which are extendible into or retractable from a rack to deliver or retrieve the load object from the storage rack. The telescoping plate members are driven by a motor during their extending and retracting movement and a brake is provided to hold the plates in a fixed location when they are not moving. Various condition sensors are also provided including a velocity feedback sensor mounted on the motor, a sensor to indicate the presence of a load, a sensor to indicate whether the load is skewed, and a sensor to indicate whether a rack into which a load is to be deposited is already full.
The motor, brake and condition sensing devices all require electrical energy to operate either in the form of power for the motor and brake or in the form of electrical control signals. For supplying the power and transmitting the signals, storage and retrieval machines use individual wires, possibly as many as 40 wires, which connect the shuttle devices mounted on the carriage to the shuttle control typically mounted on the base of the storage and retrieval machine. Very flexible wires are used due to the continual flexing and bending of the wires as the carriage is raised and lowered on the mast.
The use of wires to connect the shuttle electrical power and condition sensing devices on the movable carriage with the shuttle control on the base of the storage and retrieval machines presents several different problems. These include frequent wire breakage due to continuous cable flexing thereby requiring a high level of maintenance. High acceleration and deceleration rates of the carriage and thereby rapid operation of the storage and retrieval machine are not possible, also due to frequent wire breakage. Also, the hanging wires catch on the storage rack structures and stored load objects as the storage and retrieval machine runs along the aisle and the carriage moves vertically on the mast. Finally, the carriage is typically shipped separately from the rest of the storage and retrieval machine. Thus, in the assembly of the carriage with the other parts of the machine there is a substantial amount of labor in the field in connecting the wires between the shuttle and the control on the base of the storage and retrieval machine.